Control systems to prevent slipping or spinning of wheels are known; in some such systems, a driven wheel on which a tendency to slip or spin, or actual spinning, is sensed is braked and/or the drive torque of the vehicle is controlled to decrease the torque applied at least to the specific wheel, typically by reducing output torque from the engine. A control system of this kind is described in German Patent Disclosure Document DE-OS No. 31 27 302. In accordance with this disclosure, a wheel is braked if the wheel has a tendency to spin or slip; additionally, upon sensing a tendency of two driven wheels to spin or slip, a control signal is generated which reduces the torque output of the engine. The tendency to spin or slip is sensed by comparing speed signals or acceleration signals of the driven wheels with reference signals and, if a certain limiting or threshold value is exceeded, a tendency to slip or spin is indicated. The slip signals are obtained by comparing wheel speeds of the driven wheels with wheel speeds of non-driven or rolling wheels. As an equivalent, the wheel speed of the rolling wheels is averaged to obtain an average speed signal or, rather, a derived speed signal. The averaged or the derived speed signal is then used as a reference value or a reference speed with which the speed of the driven wheel, or driven wheels, is, or are, compared.
Under some conditions, the rolling wheels may operate at speeds, or be subjected to rotation which is not representative of vehicle speed, so that the reference is distorted.